Abstract:
With muon spin rotation (μSR) we studied the transition between the orthorhombic antiferromagnetic (o-AF) and the tetragonal antiferromagnetic (t-AF) states of a weakly underdoped Ba1−x K x Fe2As2 single crystal. We observed some characteristic changes of the magnitude and the orientation of the magnetic field at the muon site which, due to the fairly high point symmetry of the latter, allow us to identify the magnetic structure of the t-AF state. It is the so-called, inhomogeneous double-Q magnetic structure with c-axis–oriented moments which has a vanishing magnetic moment on half of the Fe sites.
